#include "bn.h"

#ifndef WITH_LIBCRYPTO
//FIXME Not checked on threadsafety yet; after checking please remove this line
/* crypto/bn/bn_div.c */
/* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
 * All rights reserved.
 *
 * This package is an SSL implementation written
 * by Eric Young (eay@cryptsoft.com).
 * The implementation was written so as to conform with Netscapes SSL.
 *
 * This library is free for commercial and non-commercial use as long as
 * the following conditions are aheared to.  The following conditions
 * apply to all code found in this distribution, be it the RC4, RSA,
 * lhash, DES, etc., code; not just the SSL code.  The SSL documentation
 * included with this distribution is covered by the same copyright terms
 * except that the holder is Tim Hudson (tjh@cryptsoft.com).
 *
 * Copyright remains Eric Young's, and as such any Copyright notices in
 * the code are not to be removed.
 * If this package is used in a product, Eric Young should be given attribution
 * as the author of the parts of the library used.
 * This can be in the form of a textual message at program startup or
 * in documentation (online or textual) provided with the package.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *    "This product includes cryptographic software written by
 *     Eric Young (eay@cryptsoft.com)"
 *    The word 'cryptographic' can be left out if the rouines from the library
 *    being used are not cryptographic related :-).
 * 4. If you include any Windows specific code (or a derivative thereof) from
 *    the apps directory (application code) you must include an acknowledgement:
 *    "This product includes software written by Tim Hudson (tjh@cryptsoft.com)"
 *
 * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 * The license and distribution terms for any publically available version or
 * derivative of this code cannot be changed.  i.e. this code cannot simply be
 * copied and put under another distribution license
 * [including the GNU Public License.]
 */

#include <stdio.h>
#include "openssl_mods.h"
#include "bn_lcl.h"

/* The old slow way */
#if 0
int BN_div(BIGNUM *dv, BIGNUM *rem, const BIGNUM *m, const BIGNUM *d,
		   BN_CTX *ctx)
{
	int i, nm, nd;
	int ret = 0;
	BIGNUM *D;

	bn_check_top(m);
	bn_check_top(d);
	if(BN_is_zero(d))
	{
		return (0);
	}

	if(BN_ucmp(m, d) < 0)
	{
		if(rem != NULL)
		{
			if(BN_copy(rem, m) == NULL) { return (0); }
		}
		if(dv != NULL) { BN_zero(dv); }
		return (1);
	}

	BN_CTX_start(ctx);
	D = BN_CTX_get(ctx);
	if(dv == NULL) { dv = BN_CTX_get(ctx); }
	if(rem == NULL) { rem = BN_CTX_get(ctx); }
	if(D == NULL || dv == NULL || rem == NULL)
		{ goto end; }

	nd = BN_num_bits(d);
	nm = BN_num_bits(m);
	if(BN_copy(D, d) == NULL) { goto end; }
	if(BN_copy(rem, m) == NULL) { goto end; }

	/* The next 2 are needed so we can do a dv->d[0]|=1 later
	 * since BN_lshift1 will only work once there is a value :-) */
	BN_zero(dv);
	bn_wexpand(dv, 1);
	dv->top = 1;

	if(!BN_lshift(D, D, nm - nd)) { goto end; }
	for(i = nm - nd; i >= 0; i--)
	{
		if(!BN_lshift1(dv, dv)) { goto end; }
		if(BN_ucmp(rem, D) >= 0)
		{
			dv->d[0] |= 1;
			if(!BN_usub(rem, rem, D)) { goto end; }
		}
		/* CAN IMPROVE (and have now :=) */
		if(!BN_rshift1(D, D)) { goto end; }
	}
	rem->neg = BN_is_zero(rem) ? 0 : m->neg;
	dv->neg = m->neg ^ d->neg;
	ret = 1;
end:
	BN_CTX_end(ctx);
	return (ret);
}

#else

#if !defined(NO_ASM) && !defined(NO_INLINE_ASM) && !defined(PEDANTIC) && !defined(BN_DIV3W)
# if defined(__GNUC__) && __GNUC__>=2
#  if defined(__i386) || defined (__i386__)
/*
 * There were two reasons for implementing this template:
 * - GNU C generates a call to a function (__udivdi3 to be exact)
 *   in reply to ((((BN_ULLONG)n0)<<BN_BITS2)|n1)/d0 (I fail to
 *   understand why...);
 * - divl doesn't only calculate quotient, but also leaves
 *   remainder in %edx which we can definitely use here:-)
 *
 *                   <appro@fy.chalmers.se>
 */
#  define bn_div_words(n0,n1,d0)        \
    ({  __asm__ volatile (          \
                                    "divl	%4"           \
                                    : "=a"(q), "=d"(rem)        \
                                    : "a"(n1), "d"(n0), "g"(d0) \
                                    : "cc");            \
        q;                  \
    })
#  define REMAINDER_IS_ALREADY_CALCULATED
#  endif /* __<cpu> */
# endif /* __GNUC__ */
#endif /* NO_ASM */

int BN_div(BIGNUM *dv, BIGNUM *rm, const BIGNUM *num, const BIGNUM *divisor,
		   BN_CTX *ctx)
{
	int norm_shift, i, j, loop;
	BIGNUM *tmp, wnum, *snum, *sdiv, *res;
	BN_ULONG *resp, *wnump;
	BN_ULONG d0, d1;
	int num_n, div_n;

	bn_check_top(num);
	bn_check_top(divisor);

	if(BN_is_zero(divisor))
	{
		return (0);
	}

	if(BN_ucmp(num, divisor) < 0)
	{
		if(rm != NULL)
		{
			if(BN_copy(rm, num) == NULL) { return (0); }
		}
		if(dv != NULL) { BN_zero(dv); }
		return (1);
	}

	BN_CTX_start(ctx);
	tmp = BN_CTX_get(ctx);
	snum = BN_CTX_get(ctx);
	sdiv = BN_CTX_get(ctx);
	if(dv == NULL)
		{ res = BN_CTX_get(ctx); }
	else    { res = dv; }
	if(sdiv == NULL || res == NULL) { goto err; }
	tmp->neg = 0;

	/* First we normalise the numbers */
	norm_shift = BN_BITS2 - ((BN_num_bits(divisor)) % BN_BITS2);
	BN_lshift(sdiv, divisor, norm_shift);
	sdiv->neg = 0;
	norm_shift += BN_BITS2;
	BN_lshift(snum, num, norm_shift);
	snum->neg = 0;
	div_n = sdiv->top;
	num_n = snum->top;
	loop = num_n - div_n;

	/* Lets setup a 'window' into snum
	 * This is the part that corresponds to the current
	 * 'area' being divided */
	BN_init(&wnum);
	wnum.d =  &(snum->d[loop]);
	wnum.top = div_n;
	wnum.dmax = snum->dmax + 1; /* a bit of a lie */

	/* Get the top 2 words of sdiv */
	/* i=sdiv->top; */
	d0 = sdiv->d[div_n - 1];
	d1 = (div_n == 1) ? 0 : sdiv->d[div_n - 2];

	/* pointer to the 'top' of snum */
	wnump = &(snum->d[num_n - 1]);

	/* Setup to 'res' */
	res->neg = (num->neg ^ divisor->neg);
	if(!bn_wexpand(res, (loop + 1))) { goto err; }
	res->top = loop;
	resp = &(res->d[loop - 1]);

	/* space for temp */
	if(!bn_wexpand(tmp, (div_n + 1))) { goto err; }

	if(BN_ucmp(&wnum, sdiv) >= 0)
	{
		if(!BN_usub(&wnum, &wnum, sdiv)) { goto err; }
		*resp = 1;
		res->d[res->top - 1] = 1;
	}
	else
		{ res->top--; }
	resp--;

	for(i = 0; i < loop - 1; i++)
	{
		BN_ULONG q, l0;
#if defined(BN_DIV3W) && !defined(NO_ASM)
		BN_ULONG bn_div_3_words(BN_ULONG *, BN_ULONG, BN_ULONG);
		q = bn_div_3_words(wnump, d1, d0);
#else
		BN_ULONG n0, n1, rem = 0;

		n0 = wnump[0];
		n1 = wnump[-1];
		if(n0 == d0)
			{ q = BN_MASK2; }
		else            /* n0 < d0 */
		{
#ifdef BN_LLONG
			BN_ULLONG t2;

#if defined(BN_LLONG) && defined(BN_DIV2W) && !defined(bn_div_words)
			q = (BN_ULONG)(((((BN_ULLONG)n0) << BN_BITS2) | n1) / d0);
#else
			q = bn_div_words(n0, n1, d0);
#endif

#ifndef REMAINDER_IS_ALREADY_CALCULATED
			/*
			 * rem doesn't have to be BN_ULLONG. The least we
			 * know it's less that d0, isn't it?
			 */
			rem = (n1 - q * d0)&BN_MASK2;
#endif
			t2 = (BN_ULLONG)d1 * q;

			for(;;)
			{
				if(t2 <= ((((BN_ULLONG)rem) << BN_BITS2) | wnump[-2]))
					{ break; }
				q--;
				rem += d0;
				if(rem < d0) { break; }  /* don't let rem overflow */
				t2 -= d1;
			}
#else /* !BN_LLONG */
			BN_ULONG t2l, t2h, ql, qh;

			q = bn_div_words(n0, n1, d0);
#ifndef REMAINDER_IS_ALREADY_CALCULATED
			rem = (n1 - q * d0)&BN_MASK2;
#endif

#ifdef BN_UMULT_HIGH
			t2l = d1 * q;
			t2h = BN_UMULT_HIGH(d1, q);
#else
			t2l = LBITS(d1);
			t2h = HBITS(d1);
			ql = LBITS(q);
			qh = HBITS(q);
			mul64(t2l, t2h, ql, qh); /* t2=(BN_ULLONG)d1*q; */
#endif

			for(;;)
			{
				if((t2h < rem) ||
						((t2h == rem) && (t2l <= wnump[-2])))
					{ break; }
				q--;
				rem += d0;
				if(rem < d0) { break; }  /* don't let rem overflow */
				if(t2l < d1) { t2h--; }
				t2l -= d1;
			}
#endif /* !BN_LLONG */
		}
#endif /* !BN_DIV3W */

		l0 = bn_mul_words(tmp->d, sdiv->d, div_n, q);
		wnum.d--;
		wnum.top++;
		tmp->d[div_n] = l0;
		for(j = div_n + 1; j > 0; j--)
			if(tmp->d[j - 1]) { break; }
		tmp->top = j;

		j = wnum.top;
		BN_sub(&wnum, &wnum, tmp);

		snum->top = snum->top + wnum.top - j;

		if(wnum.neg)
		{
			q--;
			j = wnum.top;
			BN_add(&wnum, &wnum, sdiv);
			snum->top += wnum.top - j;
		}
		*(resp--) = q;
		wnump--;
	}
	if(rm != NULL)
	{
		BN_rshift(rm, snum, norm_shift);
		rm->neg = num->neg;
	}
	BN_CTX_end(ctx);
	return (1);
err:
	BN_CTX_end(ctx);
	return (0);
}

#endif

/* rem != m */
int BN_mod(BIGNUM *rem, const BIGNUM *m, const BIGNUM *d, BN_CTX *ctx)
{
#if 0 /* The old slow way */
	int i, nm, nd;
	BIGNUM *dv;

	if(BN_ucmp(m, d) < 0)
		{ return ((BN_copy(rem, m) == NULL) ? 0 : 1); }

	BN_CTX_start(ctx);
	dv = BN_CTX_get(ctx);

	if(!BN_copy(rem, m)) { goto err; }

	nm = BN_num_bits(rem);
	nd = BN_num_bits(d);
	if(!BN_lshift(dv, d, nm - nd)) { goto err; }
	for(i = nm - nd; i >= 0; i--)
	{
		if(BN_cmp(rem, dv) >= 0)
		{
			if(!BN_sub(rem, rem, dv)) { goto err; }
		}
		if(!BN_rshift1(dv, dv)) { goto err; }
	}
	BN_CTX_end(ctx);
	return (1);
err:
	BN_CTX_end(ctx);
	return (0);
#else
	return (BN_div(NULL, rem, m, d, ctx));
#endif
}

#endif
